30.The iron content of foods can be determined by dissolving them in acid (forming ), reducing the iron(II) to iron(I), and titrating with cerium(IV):

 Identify the two half-reactions in the above reaction.
(A)
(B)
(C)
(D)

26.For a particular first-order reaction, it takes 48 minutes for the concentration of the reactant to decrease to 25% of its initial value. What is the value for rate constant for the reaction? (A) (B) (C)(D)

27.The reaction: 2 HI→ H2 + I2, is second order and the rate constant at 800 K is . How long will it take for 8.00 x mol/L of HI to decrease to one-fourth of its initial concentration? (A) 0.619s (B) 124 s (C) 387s (D) 429 s

28.What are the coefficients in front of and Cu(s) when the following redox equation is balanced in an acidic solution: (A) 2, 3 (B) 2,6 (C) 3,4 (D) 3,6

29.Determine the number of water molecules necessary to balance the following chemical equation. (A) 3 (B) 5 (C) 7 (D) 14

31.For the hypothetical reaction . For this reaction, if the value of x is 4, then the value of y =_________. (A)1 (B)2 (C)3 (D)4

32. Which of the following reactions should be spontaneous under standard conditions? (A) I and II are both nonsponta (B) I is nonspontaneous and I is spontaneous. (C) I is spontaneous and II is nonspontaneous. (D) I and II are both spontaneous.

33.At a certain temperature, Kc equals 1.4 x 102 for the reaction:2CO(g)+O2(g)⇌2 CO2(g) If a 2.50-L flask contains 0.400 mol of CO2 and 0.100 mol of O2 at equilibrium, how many moles of CO are also present in the flask? (A) 0.422 mol (B) 0.169 mol (C) 0.107 mol (D) 0.0114mol

34.The following pictures represent aqueous solutions of binary acids of the type HA where the water molecules have been omitted for clarity.Determine the strongest acid of the set. (A)A(B)B (C)C (D)D

35.What is the second stepwise equilibrium constant expression for phosphoric acid H3PO4? (A) (B) (C) (D)

36.Sodium reacts violently with water according to the equation: 2 Na(s) + 2 H2O(l)→ 2 NaOH(aq) +H2(g) The resulting solution has a higher temperature than the water prior to the addition of sodium. What are the signs of △H° and △S° for this reaction? (A) △H° is negative and △S° is negative. (B) △H° is negative and △S° is positive. (C) △H° is positive and △S° is negative. (D) △H° is positive and △S° is positive.